With the rapid development of modern mobile communications, more requirements are raised for base station antennas, particularly for bandwidth characteristics and miniaturization. Downsizing in antennas becomes more demanding due to the great density of networks and public increasing sensitivity towards electromagnetic wave pollution. In addition, such engineering factors as wind resistance and convenience for installation also require reduction in size of antennas.
A base station antenna is made up primarily of reflecting plate, drive mechanism, radiation unit and feed network, the reflecting plate having the ability to improve electromagnetic wave characteristics, particularly beam characteristics, thus being a significant part of the base station antenna playing a major role in forming directional diagram. Generally, the bigger reflecting plate gives better ratio performance but narrower beam width. A base plate of conventional directional antennas is required to be about ¼ wavelength bigger than the radiation device, which means it is rather big in overall size. For example, one kind of reflecting plate is designed with a horizontal tilting plate corresponding to multi-resonant frequencies wherein operating bandwidth is wide and consistency of directional diagram quite satisfactory, which yet results in big-size antenna. The other kind is a horizontal plate relatively small in size, but the antenna is still quite large due to such components as phase shifter and drive mechanism. To a base station antenna, structure of the reflecting plate influences structure of the antenna, similarly, the size determines the size.
In conclusion, many elements affect miniaturization of a base station antenna, such as height of radiation device, structure of phase shifter, drive mechanism, reflecting plate and the whole unit, structure of the reflecting plate particularly. A new type of antenna structure is therefore in pressing need to deal with the issue of miniaturization.